JP2003282596A - Method for manufacturing nitride semiconductor device and nitride semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a nitride semiconductor device capable of manufacturing the nitride semiconductor device, whose heat radiating performance is superior, at a low cost with a satisfactory yield. <P>SOLUTION: This nitride semiconductor device comprises a process for laminating a multilayer nitride semiconductor layer 2 on a supporting substrate 1, a process for forming a field effect transistor including gate wiring 8 and source/drain wirings 9 and 10 on the multilayer nitride semiconductor layer 2, a process for forming a thick film protecting film 11 on the multilayer nitride semiconductor layer 2 so that the field effect transistor can be covered, and a process for removing the supporting substrate 1 by wet etching. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a nitride semiconductor device and a nitride semiconductor device, and more specifically to a method for manufacturing a nitride semiconductor device excellent in heat dissipation and a nitride semiconductor device.

[0002]

2. Description of the Related Art In recent years, a nitride semiconductor device using a nitride semiconductor, which is a kind of compound semiconductor, has been receiving attention.
This nitride semiconductor is made of gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), and mixed crystal semiconductors thereof. Nitride semiconductor devices have a higher electron mobility than silicon semiconductor devices and are capable of high-speed signal processing, and are being researched and developed for various applications. In particular, In _X Ga _{1 -X} N
It is also known that a high-luminance light-emitting device can be obtained by using a crystal represented by the composition formula in 1) as a light-emitting layer.

This nitride semiconductor is manufactured by epitaxially growing a single crystal film of a nitride semiconductor on a substrate crystal of a supporting substrate and laminating the single crystal film.
In the present invention, this laminated body of single crystal films of the nitride semiconductor is referred to as a nitride semiconductor layer. The characteristics of nitride semiconductors are
It is largely influenced by the density of crystal defects in the single crystal film. Therefore, as the supporting substrate material used when forming the nitride semiconductor, a material having the same crystal structure as the nitride semiconductor crystal epitaxially grown thereon, a lattice constant, and a physical constant such as a thermal expansion coefficient is preferable. .
From the above viewpoints, it is ideal to use, for example, a GaN single crystal as a supporting substrate material, but it is extremely difficult to produce a large GaN crystal, and it has not been realized yet.

Therefore, a nitride semiconductor is manufactured using a sapphire substrate or a silicon carbide (SiC) substrate having a physical property constant closer to that of a semiconductor crystal to be epitaxially grown. However, in the present circumstances, these supporting substrate materials are very expensive, and there are many problems such that a large-diameter wafer cannot be prepared.

Silicon substrates and gallium arsenide (GaAs) substrates are available as supporting substrate materials, which are much cheaper than the above-mentioned sapphire substrate and SiC substrate and which can be used to prepare large-diameter wafers. However, since the physical constants of these substrates are significantly different from the physical constants of the semiconductor crystal to be epitaxially grown, they were not suitable as a supporting substrate material used for producing a nitride semiconductor. However, due to recent research and development, for example, silicon substrates and G
By forming a buffer layer such as a zinc oxide (ZnO) layer on an aAs substrate and growing an epitaxial film of a nitride semiconductor on the buffer layer, it is possible to obtain a nitride semiconductor layer having excellent characteristics. It has become to. Also,
As a result of further technological development, it is becoming possible to directly form a nitride semiconductor layer having excellent characteristics on a silicon substrate or a GaAs substrate.

Usually, in manufacturing a nitride semiconductor device, a semiconductor element is formed on a nitride semiconductor substrate manufactured using a supporting substrate. As a method of manufacturing a nitride semiconductor substrate, for example, Japanese Patent Application Laid-Open No. 9-
There is a manufacturing method disclosed in JP-A 208396 and JP-A 11-145057. The nitride semiconductor substrates manufactured by these manufacturing methods are each formed to have a thickness of about several hundreds of μm in order to ensure the rigidity thereof.

However, in order to improve the reliability of the nitride semiconductor device, it is necessary to efficiently dissipate the heat generated in the active region during the operation of the nitride semiconductor device. If this heat dissipation property is not sufficiently ensured, heat will accumulate inside the nitride semiconductor device, which may cause damage.

For this reason, an attempt has been made to thin the supporting substrate by mechanical polishing after forming a semiconductor element on a multi-layered nitride semiconductor layer (Y. Ando e.
t al., International Electron Devices Meeting, Dec
ember2-5, 2001, Technical Digest, pp.381-384). A nitride semiconductor device manufactured using this manufacturing method is shown in FIG.
Shown in. As shown in the figure, on the back surface of the nitride semiconductor layer 2 on which the field effect transistor which is a semiconductor element is formed,
The support substrate 1 is located via the buffer layer 15. The thickness of the supporting substrate 1 is 50 μm, and after forming the field effect transistor on the nitride semiconductor layer 2, the supporting substrate 1 is
It is a thin plate made by mechanical polishing. Here, on the nitride semiconductor layer 2, an element isolation region 3, a source / drain region, a gate electrode 5, a source electrode 6, and a drain electrode 7 are formed, respectively. A surface protective film 4 is formed on the main surface of the nitride semiconductor layer 2.

By using this manufacturing method, it becomes possible to reduce the thickness of the multi-layered nitride semiconductor layer to a thinness of several μm to several tens of μm, and further, this multi-layered nitride semiconductor layer. The thickness of the support substrate located on the back surface of the
It becomes possible to reduce the thickness to about μm. As a result, it becomes possible to manufacture a nitride semiconductor device having improved heat dissipation.

[0010]

However, when the supporting substrate is thinned using the above-described mechanical polishing, it is difficult to control the polishing rate and the accompanying control of the polishing film thickness. For example, when a sapphire substrate is used, the sapphire substrate is extremely hard, so that the polishing time is very long and the polishing apparatus is significantly worn. In addition, when the wafer is warped, the thickness of the supporting substrate in the wafer surface after polishing may be non-uniform, and there is a concern that the heat dissipation characteristics of the individual elements may vary or the yield may decrease, which is preferable. Absent.

Further, ideally, it is desirable to completely remove the supporting substrate, but when mechanical polishing is performed, there is a high possibility that the wafer will be physically damaged, and the supporting substrate is completely removed. Is extremely difficult. For this reason, polishing must be completed with the supporting substrate having a low thermal conductivity remaining on the back surface of the nitride semiconductor device. Therefore, it cannot be said that the heat dissipation is sufficient.

Therefore, the present invention has been made to solve the above-mentioned problems, and a method of manufacturing a nitride semiconductor device capable of providing a nitride semiconductor device excellent in heat dissipation at a low cost and a high yield. Another object of the present invention is to provide a nitride semiconductor device.

[0013]

According to a first aspect of the present invention, there is provided a method for manufacturing a nitride semiconductor device, which comprises a step of forming a multilayer nitride semiconductor layer on a supporting substrate, and a multilayer nitride semiconductor layer. The method includes the steps of forming a semiconductor element on the top and removing the supporting substrate after the formation of the semiconductor element.

As in the present manufacturing method, the semiconductor element is formed in a state in which the multi-layered nitride semiconductor layers are laminated on the supporting substrate, so that the nitride semiconductor layer of the nitride semiconductor device is thinner than the conventional one. Can be formed. Moreover,
By removing the supporting substrate after forming the semiconductor element, it becomes possible to manufacture a nitride semiconductor device having no supporting substrate. Therefore, it is possible to provide a nitride semiconductor device having excellent heat dissipation. A chemical method is more effective as a method for completely removing the supporting substrate.

In the method for manufacturing a nitride semiconductor device according to the first aspect of the present invention, it is preferable that:
The method includes a step of forming a thick protective film on the multilayer nitride semiconductor layer so as to cover the semiconductor element before removing the supporting substrate, and a step of removing the thick protective film after removing the supporting substrate.

By thus forming the thick protective film so as to cover the semiconductor element and then removing the supporting substrate,
It is possible to secure the rigidity of the thin-filmed multi-layered nitride semiconductor layer and protect the already formed semiconductor element. As a result, it becomes possible to manufacture a nitride semiconductor device having a high yield and excellent heat dissipation.

In the method for manufacturing a nitride semiconductor device according to the first aspect of the present invention, preferably,
A step of forming a heat dissipation layer containing metal or carbon as a main component is provided on the surface of the multilayer nitride semiconductor layer exposed by removing the support substrate.

This makes it possible to form a heat dissipation layer having excellent heat dissipation so as to be in direct contact with the nitride semiconductor layer of the nitride semiconductor device, and to manufacture a nitride semiconductor device having more excellent heat dissipation. Will be possible.

In the method of manufacturing a nitride semiconductor device according to the first aspect of the present invention, preferably, the thickness of the multilayer nitride semiconductor layer formed on the supporting substrate is 50 μm.
m or less.

As described above, by manufacturing a nitride semiconductor device using the present manufacturing method, it is possible to reduce the thickness of the multilayer nitride semiconductor layer in which the semiconductor element is formed to 50 μm or less, which is excellent. It is possible to manufacture a nitride semiconductor device having heat dissipation.

In the method for manufacturing a nitride semiconductor device according to the first aspect of the present invention, more preferably, the thickness of the multilayer nitride semiconductor layer formed on the supporting substrate is 1
It is set to 0 μm or less.

As described above, by manufacturing a nitride semiconductor device using this manufacturing method, it becomes possible to reduce the thickness of a multilayer nitride semiconductor layer in which a semiconductor element is formed to 10 μm or less. It is possible to manufacture a nitride semiconductor device having excellent heat dissipation.

In the method for manufacturing a nitride semiconductor device according to the first aspect of the present invention, preferably, the supporting substrate is removed by etching the supporting substrate.

As described above, by using the etchable support substrate as the support substrate, the support substrate can be easily and completely removed by etching.

In the method for manufacturing a nitride semiconductor device according to the first aspect of the present invention, it is preferable that:
The method further includes a step of previously forming an uneven shape on the surface of the support substrate on which the multilayer nitride semiconductor layers are formed.

By thus forming fine irregularities on the surface of the supporting substrate in advance, it becomes possible to impart irregularities on the back surface of the multilayer nitride semiconductor layer formed on the supporting substrate. This makes it possible to increase the contact area at the interface between the back surface of the multi-layered nitride semiconductor layer and the heat dissipation layer formed after removing the supporting substrate, so that the nitride semiconductor with even higher heat dissipation performance can be obtained. It becomes possible to manufacture the device. The shape of the unevenness to be applied may be, for example, a houndstooth checkered unevenness or a stripe-shaped unevenness.

In the method for manufacturing a nitride semiconductor device according to the first aspect of the present invention, it is preferable that:
The method includes a step of forming an intermediate layer between the support substrate and the multi-layered nitride semiconductor layer, and the intermediate layer is removed by etching to remove the support substrate.

This makes it possible to easily separate the supporting substrate from the multi-layered nitride semiconductor layer by removing the intermediate layer. Therefore, the supporting substrate can be reused, and the nitride semiconductor device can be manufactured at a lower cost. Further, by suppressing the thickness of the intermediate layer to be thin, the time required for separating the supporting substrate and the nitride semiconductor device can be shortened, so that the supporting substrate separating process can be performed at low cost.

In the method for manufacturing a nitride semiconductor device according to the first aspect of the present invention, it is preferable that:
The method further comprises the step of previously forming an uneven shape on the surface of the intermediate layer on which the multilayer nitride semiconductor layer is formed.

By thus forming fine irregularities on the surface of the intermediate layer in advance, it becomes possible to make the back surface of the multilayer nitride semiconductor layer formed on the intermediate layer irregular. . This makes it possible to increase the contact area at the interface between the back surface of the multilayer nitride semiconductor layer and the heat dissipation layer formed after the removal of the support substrate, and thus the nitride semiconductor device having even higher heat dissipation performance. Can be manufactured. The shape of the unevenness to be applied may be, for example, a houndstooth checkered unevenness or a stripe-shaped unevenness.

A method of manufacturing a nitride semiconductor device according to the second aspect of the present invention includes a step of forming a heat dissipation layer containing metal or carbon as a main component on a supporting substrate, and a multilayer nitride semiconductor device on the heat dissipation layer. The method includes a step of stacking layers, a step of forming a semiconductor element on a multilayer nitride semiconductor layer, and a step of removing a supporting substrate after the semiconductor element is formed.

As in the present manufacturing method, a heat dissipation layer is provided on a supporting substrate, and a semiconductor element is formed in a state in which a multilayer nitride semiconductor layer is further stacked on the heat dissipation layer to form a nitride of a nitride semiconductor device. The semiconductor layer can be formed thinner than before. Furthermore, by removing the supporting substrate after forming the semiconductor element, it becomes possible to manufacture a nitride semiconductor device having no supporting substrate. Further, by forming the heat dissipation layer between the support substrate and the multi-layered nitride semiconductor layer in advance, it is not necessary to newly form the heat dissipation layer on the back surface of the multi-layered nitride semiconductor layer after separating the support substrate. Therefore, it is possible to provide a nitride semiconductor device having excellent heat dissipation.

In the method for manufacturing a nitride semiconductor device according to the second aspect of the present invention, preferably,
The method includes a step of forming a thick protective film on the multilayer nitride semiconductor layer so as to cover the semiconductor element before removing the supporting substrate, and a step of removing the thick protective film after removing the supporting substrate.

As described above, by removing the supporting substrate after forming the thick protective film so as to cover the semiconductor element,
It is possible to secure the rigidity of the thin-filmed multi-layered nitride semiconductor layer and protect the already formed semiconductor element. As a result, it becomes possible to manufacture a nitride semiconductor device having a high yield and excellent heat dissipation.

In the method for manufacturing a nitride semiconductor device according to the second aspect of the present invention described above, preferably, the thickness of the multilayer nitride semiconductor layer formed on the heat dissipation layer is 50 μm.
m or less.

As described above, by manufacturing a nitride semiconductor device using the present manufacturing method, it becomes possible to reduce the thickness of the multilayer nitride semiconductor layer in which a semiconductor element is formed to 50 μm or less, which is excellent. It is possible to manufacture a nitride semiconductor device having heat dissipation.

In the method for manufacturing a nitride semiconductor device according to the second aspect of the present invention, more preferably, the thickness of the multilayer nitride semiconductor layer formed on the heat dissipation layer is 1
It is set to 0 μm or less.

As described above, by manufacturing a nitride semiconductor device using the present manufacturing method, it becomes possible to reduce the thickness of a multilayer nitride semiconductor layer in which a semiconductor element is formed to 10 μm or less, which is further excellent. It is possible to manufacture a nitride semiconductor device having excellent heat dissipation.

In the method for manufacturing a nitride semiconductor device according to the second aspect of the present invention, the heat dissipation layer is preferably made of a material having a thermal conductivity of 3 W / cmK or more.

As described above, the heat dissipation layer is formed of a material having a thermal conductivity of 3 W / cmK or more, which is the thermal conductivity of silicon carbide, so that the silicon carbide substrate is used as the supporting substrate for nitriding. It is possible to manufacture a nitride semiconductor device having a heat dissipation performance equal to or higher than that of the object semiconductor device.

In the method for manufacturing a nitride semiconductor device according to the second aspect of the present invention, it is preferable that:
The method further comprises a step of previously forming an uneven shape on the surface of the heat dissipation layer on which the multilayer nitride semiconductor layer is formed.

Thus, by forming fine irregularities on the surface of the heat dissipation layer in advance, the back surface of the multilayer nitride semiconductor layer formed on the heat dissipation layer can be made irregular. . This makes it possible to increase the contact area at the interface between the back surface of the multilayer nitride semiconductor layer and the heat dissipation layer, and thus it is possible to manufacture a nitride semiconductor device having higher heat dissipation performance. The shape of the unevenness to be applied may be, for example, a houndstooth checkered unevenness or a stripe-shaped unevenness.

In the method for manufacturing a nitride semiconductor device according to the second aspect of the present invention, the support substrate is preferably removed by etching the support substrate.

As described above, by using the etchable support substrate as the support substrate, the support substrate can be easily and completely removed by etching.

In the method for manufacturing a nitride semiconductor device according to the second aspect of the present invention, it is preferable that:
A step of forming an intermediate layer different from the heat dissipation layer between the support substrate and the heat dissipation layer is provided, and the support substrate is removed by removing the intermediate layer by etching.

This enables the supporting substrate to be easily separated from the multi-layered nitride semiconductor layer by removing the intermediate layer. Therefore, the supporting substrate can be reused, and the nitride semiconductor can be manufactured at a lower cost. Further, by suppressing the thickness of the intermediate layer to be thin, the time required for separating the supporting substrate and the nitride semiconductor device can be shortened, so that the supporting substrate separating process can be performed at low cost.

A nitride semiconductor device according to the present invention is a nitride semiconductor device having a multilayer nitride semiconductor layer on which a semiconductor element is formed, and the multilayer nitride semiconductor layer has a thickness of 50 μm or less, It is characterized in that a heat dissipation layer containing metal or carbon as a main component is arranged so as to be in contact with the back surface of the multi-layered nitride semiconductor layer.

As described above, by thinning the multi-layered nitride semiconductor layer of the nitride semiconductor device to 50 μm or less, a nitride semiconductor device excellent in heat dissipation is obtained. Further, by forming the heat dissipation layer so as to be in direct contact with the multi-layered nitride semiconductor layer thinned to 50 μm or less, the heat dissipation can be further improved.

In the nitride semiconductor device according to the present invention described above, preferably, the thickness of the multilayer nitride semiconductor layer is 1 or less.
It is 0 μm or less.

As described above, by thinning the multi-layered nitride semiconductor layer of the nitride semiconductor device to 10 μm or less, a nitride semiconductor device having an excellent heat dissipation property can be obtained. Further, by forming the heat dissipation layer so as to be in direct contact with the multi-layered nitride semiconductor layer thinned to 10 μm or less, the heat dissipation can be further improved.

In the nitride semiconductor device according to the present invention, the heat dissipation layer is preferably made of a material having a thermal conductivity of 3 W / cmK or more.

As described above, the heat dissipation layer is made of a material having a thermal conductivity of 3 W / cmK or more, which is the thermal conductivity of silicon carbide, so that the silicon carbide substrate is used as the supporting substrate for nitriding. It is possible to manufacture a nitride semiconductor device having a heat dissipation performance equal to or higher than that of the object semiconductor device.

In the above-described nitride semiconductor device according to the present invention, preferably, the interface between the back surface of the multilayer nitride semiconductor layer and the heat dissipation layer is uneven.

As described above, since the interface between the back surface of the multilayer nitride semiconductor layer and the heat dissipation layer is uneven, the contact area at the interface is increased, and a nitride semiconductor device having higher heat dissipation performance is manufactured. It becomes possible to do. In addition,
As the shape of the unevenness to be applied, for example, a houndstooth checkered unevenness or a stripe-shaped unevenness can be considered.

[0055]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIGS. 1 to 6 are sectional views showing a method of manufacturing a nitride semiconductor device according to a first embodiment of the present invention. FIG. 1 shows a state after the formation of a multilayer nitride semiconductor layer, and FIG. 2 shows a state after the formation of a semiconductor element.
Indicates after the thick protective film is formed. Further, FIG. 4 shows after removing the supporting substrate, FIG. 5 shows after forming the heat dissipation layer, and FIG. 6 shows after removing the thick protective film. Hereinafter, with reference to the drawings, the method for manufacturing the nitride semiconductor device in the present embodiment will be described in detail in order.

First, as shown in FIG. 1, a supporting substrate 1 is prepared, and a multi-layered nitride semiconductor layer 2 is formed on the main surface of the supporting substrate 1. Here, as the supporting substrate 1, it is preferable to use a silicon substrate or a GaAs substrate. this is,
This is because it is desirable to use a support substrate that can be selectively and easily removed by etching for the epitaxial growth of the nitride semiconductor layer and for the process of removing the support substrate described later. The multilayer nitride semiconductor layer 2 formed on the support substrate 1 preferably has a thickness of 50 μm or less, and more preferably 10 μm from the viewpoint of heat dissipation.
The thickness is m or less.

Next, as shown in FIG. 2, a field effect transistor, which is a semiconductor element, is formed on the multi-layered nitride semiconductor layer 2. Specifically, the element isolation region 3 is formed, the source / drain regions are formed, and the gate electrode 5, the source electrode 6, and the drain electrode 7 are formed. Further, the surface protection film 4 for protecting the surface of the nitride semiconductor device, the wirings 8, 9 and 10 having an air bridge structure, etc. may be provided.

Next, as shown in FIG. 3, a thick protective film 11 is formed on the nitride semiconductor layer 2 so as to cover the field effect transistor. This is for maintaining the rigidity of the nitride semiconductor layer 2 in the supporting substrate removing process described later, and at the same time for protecting the field effect transistor in the supporting substrate removing process.
The material for the thick protective film 11 may be any material that can be selectively removed after removing the supporting substrate, and for example, an organic resist, wax, silicon oxide film, polyimide film, metal film or the like can be used. The thickness of the thick protective film 11 is
The thickness is sufficient as long as it covers the electrodes 5, 6, 7 and wirings 8, 9, 10 of the semiconductor element and the rigidity of the multilayer nitride semiconductor layer 2 is sufficiently maintained, and is preferably 100 μm or more.

Continuing, as shown in FIG.
Are removed by etching. The removing process of the supporting substrate may be any removing process as long as it is a chemical method, but it is particularly preferably performed by wet etching. If a silicon substrate or a GaAs substrate is used as the supporting substrate 1, the supporting substrate 1 can be selectively and easily removed with, for example, hydrofluoric nitric acid or aqua regia. Through the supporting substrate removing process, the supporting substrate 1 is completely melted and removed from the nitride semiconductor device, and the back surface of the nitride semiconductor layer 2 is exposed.

Next, as shown in FIG. 5, a heat dissipation layer 12 made of metal or carbon is formed on the surface of the multilayer nitride semiconductor layer 2 exposed by the above-mentioned supporting substrate removing process. The material of the heat dissipation layer 12 is, for example, Au.
A metal containing Au or Sn, or a material containing carbon as a main component such as amorphous carbon, diamond, fullerene, or carbon nanotube is preferable. Further, the thickness of the heat dissipation layer 12 may be such that the rigidity of the nitride semiconductor layer 2 is maintained and at the same time the heat is sufficiently released to the outside when the field effect transistor operates.

Further, the thick protective film 11 covering the upper part of the multilayer nitride semiconductor layer 2 is removed by etching or the like. As a result, the nitride semiconductor device having the structure shown in FIG. 6 is obtained. In addition, as long as the rigidity of the nitride semiconductor layer 2 is sufficiently maintained, the thick protective film 11 may be removed before the heat dissipation layer 12 is formed. When each element needs to be cut out from the wafer, it may be cut out using a scriber or the like before or after forming the heat dissipation layer 12, and then the thick protective film 12 may be removed.

Through the above manufacturing steps, a nitride semiconductor device is obtained in which the supporting substrate is completely removed and the heat dissipation layer is formed so as to be in direct contact with the back surface of the nitride semiconductor layer. Further, it is possible to obtain a nitride semiconductor device in which the thickness of the nitride semiconductor layer is significantly thinner than the conventional one. As a result, the distance from the active region, which is the heat generating region during operation of the nitride semiconductor device, to the heat dissipation layer is determined only by the film thickness of the nitride semiconductor layer, and by making this nitride semiconductor layer as thin as possible. It is possible to manufacture a nitride semiconductor device having excellent heat dissipation.

Further, since the conventional mechanical polishing for thinning the supporting substrate is not used, there is no fear of mechanical damage to the element. Further, by using a silicon substrate or a gallium arsenide substrate as the supporting substrate,
The wet etching makes it possible to remove the supporting substrate easily and selectively. Further, by using these supporting substrates, the nitride semiconductor devices can be easily individually cut out from the wafer. Furthermore, when a silicon substrate is used, a large-diameter wafer can be used, so that the nitride semiconductor device can be manufactured at a lower cost. Furthermore, since the thickness of the nitride semiconductor layer is determined by the film thickness of the nitride semiconductor layer during epitaxial growth, it is not necessary to obtain the in-plane nonuniformity of the supporting substrate due to the warp of the wafer in the thinning process of the supporting substrate. Thus, the nitride semiconductor device can be easily manufactured.

In order to obtain a nitride semiconductor device having further excellent heat dissipation, it is preferable to make fine irregularities on the surface of the supporting substrate 1 prepared in advance. As a result, the nitride semiconductor device having the structure shown in FIG. 7 is obtained. In this case, the support substrate 1
It becomes possible to make the back surface of the nitride semiconductor layer 2 formed above the uneven surface 2a, and increase the contact area with the heat dissipation layer 12 formed in a later step. Therefore, it becomes possible to manufacture a nitride semiconductor layer having further excellent heat dissipation. The shape of the unevenness to be applied may be any unevenness such as a houndstooth checkered pattern or a striped pattern.

(Second Embodiment) FIGS. 8 to 10 are sectional views showing a method for manufacturing a nitride semiconductor device according to a second embodiment of the present invention. FIG. 8 shows the state after the formation of the multi-layered nitride semiconductor layer, FIG. 9 shows the state after the thick protective film is formed, and FIG. The same parts as those in the first embodiment described above are designated by the same reference numerals in the drawings,
The description will not be repeated.

First, as shown in FIG. 8, the supporting substrate 1 is prepared, and the intermediate layer 13 is formed on the main surface of the supporting substrate 1. Further, immediately above the intermediate layer 13, the multilayer nitride semiconductor layer 2 is formed.
To form. Here, a sapphire substrate or a SiC substrate is used as the support substrate 1, and Z is used as the intermediate layer 13.
An nO layer is formed. As the intermediate layer, the above-mentioned Z
Other than the nO layer, an InGaP layer, an AlGaAs layer, or the like may be used. The film thickness of the intermediate layer 13 is preferably set to about 10 nm to 10 μm so that etching can be easily performed in the supporting substrate separation process described later. In addition, the multilayer nitride semiconductor layer 2 formed on the intermediate layer 13
Is preferably 50 μm or less, more preferably 10 μm or less from the viewpoint of heat dissipation.

As the subsequent steps, the same steps as those in the first embodiment described above are continued. As shown in FIG. 9, the nitride semiconductor layer 2
When the thick protective film 11 is formed so as to cover the field effect transistor formed above, the supporting substrate separation process is performed. Specifically, the intermediate layer 13 is removed by etching. The separation process of the supporting substrate (in other words, the removal process of the intermediate layer) may be any removal process as long as it is a chemical method, but it is particularly preferably performed by wet etching. When the ZnO layer is formed as the intermediate layer 13, the intermediate layer 13 can be selectively and easily removed with, for example, hydrochloric acid. As a result, the intermediate layer 13 is completely dissolved, the supporting substrate 1 is separated from the nitride semiconductor device, and the back surface of the nitride semiconductor layer 2 is exposed.

Then, the heat dissipation layer 12 is formed on the back surface of the nitride semiconductor layer 2 and the thick film protective film 11 is removed in the same manner as in the first embodiment described above to obtain the nitride semiconductor device shown in FIG. To be

Through the above manufacturing steps, a nitride semiconductor device is obtained in which the supporting substrate is completely separated and the heat dissipation layer is formed so as to be in direct contact with the back surface of the nitride semiconductor layer. Further, it is possible to obtain a nitride semiconductor device in which the thickness of the nitride semiconductor layer is significantly thinner than the conventional one. As a result, the same effect as that of the first embodiment can be obtained. Furthermore, by forming the intermediate layer thinner than in the first embodiment,
Since the supporting substrate can be separated from the nitride semiconductor device in a short time and with a small amount of chemical liquid, the nitride semiconductor device can be manufactured at a lower cost. Further, since the separated support substrate can be reused, effective use of materials, resource saving, and cost reduction of the nitride semiconductor device can be realized.

Further, as in the first embodiment, the heat dissipation performance can be further improved by making the interface between the nitride semiconductor layer and the heat dissipation layer uneven. In this case, the surface of the intermediate layer formed on the supporting substrate may be provided with irregularities in advance.

In this embodiment, the case where the sapphire substrate or the SiC substrate is used as the supporting substrate has been exemplified, but it is also possible to use the silicon substrate or the GaAs substrate as the supporting substrate. When a silicon substrate is used as the supporting substrate, a GaAs layer or a ZnO layer can be formed as the intermediate layer. On the other hand, when a GaAs substrate is used as the supporting substrate, a silicon layer, an InGaP layer, an AlGaAs layer, a ZnO layer or the like can be formed as the intermediate layer. As a result, the intermediate layer can be easily and selectively removed by wet etching, and the supporting substrate and the nitride semiconductor device can be easily separated. Further, by using these supporting substrates, the nitride semiconductor devices can be easily cut out individually from the wafer. Furthermore, since a large-diameter wafer can be used, the nitride semiconductor device can be manufactured at a lower cost.

(Third Embodiment) FIG. 11 and FIG.
FIG. 13 is a cross-sectional view showing the method for manufacturing the nitride semiconductor device in the third embodiment of the present invention. FIG. 11 shows the state after the multi-layered nitride semiconductor layer is formed, and FIG. 12 shows the state after the supporting substrate is separated. The same parts as those in the second embodiment described above are designated by the same reference numerals in the drawings, and the description thereof will not be repeated.

First, as shown in FIG. 11, the supporting substrate 1 is prepared, and the intermediate layer 13 is formed on the main surface of the supporting substrate 1.
Further, a heat dissipation layer 14 is formed directly on the intermediate layer 13,
Further, a multilayer nitride semiconductor layer 2 is formed thereon. For example, the support substrate 1 is a sapphire substrate or a SiC substrate, and the intermediate layer 13 is a ZnO layer. As the material of the heat dissipation layer 14, for example, a metal containing Au or AuSn, or a material containing carbon as a main component such as amorphous carbon, diamond, fullerene, or carbon nanotube is desirable. Further, the thickness of the heat dissipation layer 14 may be such that the rigidity of the nitride semiconductor layer 2 is maintained and at the same time the heat is sufficiently released to the outside during the operation of the field effect transistor.

The subsequent steps are the same as those in the second embodiment described above. Finally, the intermediate layer 13 is removed, and the supporting substrate 1 is separated by the nitride semiconductor device.
A nitride semiconductor device having the structure shown in is obtained.

Through the above manufacturing steps, the same effect as in the above-described second embodiment can be obtained, and by forming the heat dissipation layer in advance, it is troublesome to form the heat dissipation layer again after separating the support substrate. Can be omitted. Further, by forming the heat dissipation layer to a thickness that maintains the rigidity of the nitride semiconductor layer, it is possible to omit the step of forming and removing the thick protective film. In addition, since it is possible to perform the film forming process at high temperature necessary for forming the heat dissipation structure, annealing, plasma etching, etc. before forming the element, it is possible to protect all or part of the heat dissipation structure without adversely affecting the element. Can be formed.

As in the first and second embodiments, the heat dissipation performance can be further improved by forming the interface between the nitride semiconductor layer and the heat dissipation layer into an uneven shape. In this case, the surface of the heat dissipation layer formed on the support substrate may be provided with irregularities in advance.

In this embodiment, an intermediate layer that can be etched is formed between the supporting substrate and the multi-layered nitride semiconductor layer, and the intermediate layer is removed, as in the second embodiment. Thus, the manufacturing method using the method of separating the supporting substrate from the nitride semiconductor device has been described as an example, but like the first embodiment, the supporting substrate itself is removed by etching without providing the intermediate layer. This also makes it possible to obtain a nitride semiconductor device having a similar structure.

Further, in all of the above-mentioned embodiments, the case where the support substrate and the intermediate layer are removed by wet etching has been described as an example, but the present invention is not limited to this, and removal by dry etching is possible. Is also possible.

As described above, the above-described embodiments disclosed this time are exemplifications in all respects, and are not restrictive. The technical scope of the present invention is defined by the claims, and includes the meaning equivalent to the description of the claims and all modifications within the scope.

[0081]

According to the present invention, it becomes possible to inexpensively and easily manufacture a nitride semiconductor device which is much more excellent in heat dissipation than a conventional nitride semiconductor device. This makes it possible to provide a high-performance nitride semiconductor device with excellent reliability at low cost.

[Brief description of drawings]

FIG. 1 is a diagram for illustrating the method for manufacturing the nitride semiconductor device in the first embodiment of the present invention, which is a cross-sectional view after the formation of the nitride semiconductor layer.

FIG. 2 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the first embodiment of the present invention, which is a cross-sectional view after the formation of the semiconductor element.

FIG. 3 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the first embodiment of the present invention, which is a cross-sectional view after the thick protective film is formed.

FIG. 4 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the first embodiment of the present invention, which is a cross-sectional view after the support substrate is removed.

FIG. 5 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the first embodiment of the present invention, which is a cross-sectional view after the formation of the heat dissipation layer.

FIG. 6 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the first embodiment of the present invention, which is a cross-sectional view after the thick protective film is removed.

FIG. 7 is a cross-sectional view showing a modified example of the first embodiment of the present invention.

FIG. 8 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the second embodiment of the present invention, which is a cross-sectional view after the formation of the multilayer nitride semiconductor layers.

FIG. 9 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the second embodiment of the present invention, which is a cross-sectional view after the thick protective film is formed.

FIG. 10 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the second embodiment of the present invention, which is a cross-sectional view after the support substrate is separated.

FIG. 11 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the third embodiment of the present invention, which is a cross-sectional view after the formation of the multilayer nitride semiconductor layer.

FIG. 12 is a diagram for illustrating the method for manufacturing the nitride semiconductor device according to the third embodiment of the present invention, which is a cross-sectional view after the support substrate is separated.

FIG. 13 is a cross-sectional view of a nitride semiconductor device in which a supporting substrate is thinned by using mechanical polishing according to a conventional technique.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 support substrate, 2 multilayer nitride semiconductor layers, 2a uneven surface, 3 element isolation region, 4 surface protection film, 5 gate electrode, 6 source electrode, 7 drain electrode, 8 gate wiring, 9 source wiring, 10 drain wiring, 11 thick protective film, 12 heat dissipation layer, 13 intermediate layer, 14 heat dissipation layer.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Muneyoshi Suita             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Takuma Nanjo             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Yuji Abe             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. (72) Inventor Tetsuya Takami             2-3 2-3 Marunouchi, Chiyoda-ku, Tokyo             Inside Ryo Electric Co., Ltd. F-term (reference) 5F102 FA00 FA08 GB01 GC01 GJ02                       GJ10 GL03 GL04 GL05 GV05                       HC15

Claims (21)

[Claims] 1. A step of stacking and forming a multi-layered nitride semiconductor layer on a support substrate, a step of forming a semiconductor element on the multi-layered nitride semiconductor layer, and a step of forming the support substrate after the formation of the semiconductor element. And a step of removing the nitride semiconductor device. 2. A step of forming a thick film protective film on the multilayered nitride semiconductor layers so as to cover the semiconductor element before removing the supporting substrate, and the thick film protecting film after removing the supporting substrate. The method for manufacturing a nitride semiconductor device according to claim 1, further comprising a step of removing the protective film. 3. The method according to claim 1, further comprising the step of forming a heat dissipation layer containing metal or carbon as a main component on a surface of the multilayer nitride semiconductor layer exposed by removing the supporting substrate. A method of manufacturing a nitride semiconductor device according to item 1. 4. The method for manufacturing a nitride semiconductor device according to claim 1, wherein the multilayer nitride semiconductor layers formed on the support substrate have a thickness of 50 μm or less. 5. The method for manufacturing a nitride semiconductor device according to claim 4, wherein the multilayered nitride semiconductor layers formed on the support substrate have a thickness of 10 μm or less. 6. The method for manufacturing a nitride semiconductor device according to claim 1, wherein the supporting substrate is removed by removing the supporting substrate by etching. 7. The nitride semiconductor device according to claim 1, further comprising a step of previously forming an uneven shape on a surface of the support substrate on which the multilayer nitride semiconductor layers are formed. Production method. 8. The step of forming an intermediate layer between the support substrate and the multi-layered nitride semiconductor layer, the removal of the intermediate layer by etching removes the support substrate. 6. The method for manufacturing a nitride semiconductor device according to any one of 1 to 5. 9. The method for manufacturing a nitride semiconductor device according to claim 8, further comprising a step of previously forming an uneven shape on a surface of the intermediate layer on which the multilayer nitride semiconductor layers are formed. 10. A step of forming a heat dissipation layer containing metal or carbon as a main component on a supporting substrate, a step of forming a multilayer nitride semiconductor layer on the heat dissipation layer, and a step of forming the multilayer nitride semiconductor layer. A method of manufacturing a nitride semiconductor device, comprising: a step of forming a semiconductor element on the top; and a step of removing the supporting substrate after the formation of the semiconductor element. 11. A step of forming a thick film protective film on the multilayer nitride semiconductor layers so as to cover the semiconductor element before removing the supporting substrate, and the thick film protecting film after removing the supporting substrate. The method for manufacturing a nitride semiconductor device according to claim 10, further comprising: removing the protective film. 12. The method for manufacturing a nitride semiconductor device according to claim 10, wherein the multilayered nitride semiconductor layers formed on the heat dissipation layer have a thickness of 50 μm or less. 13. The method for manufacturing a nitride semiconductor device according to claim 12, wherein the multilayer nitride semiconductor layers formed on the heat dissipation layer have a thickness of 10 μm or less. 14. The method for manufacturing a nitride semiconductor device according to claim 10, wherein the heat dissipation layer is made of a material having a thermal conductivity of 3 W / cmK or more. 15. The nitride semiconductor device according to claim 10, further comprising a step of previously forming an uneven shape on a surface of the heat dissipation layer on which the multilayer nitride semiconductor layers are formed. Production method. 16. The support substrate is removed by removing the support substrate by etching.
16. The method for manufacturing a nitride semiconductor device according to any one of 0 to 15. 17. Between the support substrate and the heat dissipation layer,
16. The method for manufacturing a nitride semiconductor device according to claim 10, further comprising a step of forming an intermediate layer different from the heat dissipation layer, and removing the supporting substrate by removing the intermediate layer by etching. Method. 18. A nitride semiconductor device comprising a multilayered nitride semiconductor layer having a semiconductor element formed thereon, wherein the multilayered nitride semiconductor layer has a thickness of 50 μm or less, and the multilayered nitride semiconductor layer. So that it touches the back of
A nitride semiconductor device in which a heat dissipation layer containing metal or carbon as a main component is arranged. 19. The multilayer nitride semiconductor layer has a thickness of 1
19. The nitride semiconductor device according to claim 18, which has a thickness of 0 μm or less. 20. The nitride semiconductor device according to claim 18, wherein the heat dissipation layer is formed of a material having a thermal conductivity of 3 W / cmK or more. 21. The interface between the back surface of the multi-layered nitride semiconductor layer and the heat dissipation layer has an uneven shape.
0. The nitride semiconductor device according to any one of 0.